it is said that full frame aperture equivalent of 2.8 to aps-c is 4.2. does it mean that shutter speed of aps-c is one stop slower that full frame on the same aperture? given the same focal length equivalent e.g. aps-c 23mm and ff 35mm.
it is said that full frame aperture equivalent of 2.8 to aps-c is 4.2. does it mean that shutter speed of aps-c is one stop slower that full frame on the same aperture? given the same focal length equivalent e.g. aps-c 23mm and ff 35mm.
It’s built into the aperture f-number because it does, just like entrance pupil diameter does. Thus, it answers OP’s real question about why exposure isn’t changing even when the entrance pupil diameter changes: because focal length is also changing and ultimately you’re arriving at the same f/1.4 f-number.
https://en.wikipedia.org/wiki/F-number
Yes, you said: “This is not the case in this context”
I’m just talking about how focal length and entrance pupil diameter both go into the aperture f-number for the purposes of exposure. That’s literally how the f-number is mathematically defined.
How much light is collected is not the same as exposure, indeed. But it’s a component of exposure that affects the exposure.
What I wrote applies in the context of different format sizes. It also applies in the context of the same format size.
Well, I simply wanted to clarify what you presented in a way which seemed to me to be causing more confustion to OP in this context than necessary.
Basically this was the problem for me:
In the context of format comparison, it can get confusing to the OP as in this context the focal lengths collect light from the same area of the scene, not different.
We interpreted OP’s question differently. Not saying either interpretion is better or worse.